The present invention relates to means for maintaining in a closed condition doors hung by hinges on posts alongside access openings to containers such as packing cases and the like, and more especially to means for the purpose aforesaid and of the kind with catches on the ends of upright rods mounted on the fronts of the doors remote from the hinges for axial rotation by operating handles affixed to the rods for engagement of the catches in and disengagement of the catches from keepers fixed to the cabinet casing in positions to be above and below the rods when the doors are closed.
Since the containers are subjected during transport to external forces in various directions and also to internal pressures from the load carrier therein, means of the kind stated must be capable of effective resistance to either direct or transverse forces, with maximum guarantee of not permitting accidental opening of the doors during transport.
Moreover, when the container doors are open, the container structure which is then less rigid, may undergo resilient deformations due to forces applied or to irregularities in the supporting plane, so that, on closing the container doors, the catches may be presented off-centre to the keepers fixed on the upper and lower bars of the fixed container structure. For satisfactory performance of the means of the kind stated, even in such abnormal conditions, there must be engagement between the catches and the keepers, and the subsequent closing operation must cause the catches and the keepers to co-operate with one another and restore the container to its original condition prior to the resilient deformations undergone thereby.
Means of the kind stated hitherto known with catches and keepers have not been able to satisfy these requirements fully, at least with the heavier stresses sometimes encountered. In particular the use of the catches and keepers may become impossible in the presence of major deformations, which may then have to be suitably compensated before closure can proceed. The successive stresses tend to cause loosening of the catches from the keepers and to transmit excessive stresses to the operating handles and to locking means for the latter; hence adequate stability in the means of the kind stated is not always ensured. Due to the inadequacies of known means of the kind stated, it has been necessary to provide for each door, in more heavily stressed containers, intermediate closure devices in addition to the means of the kind stated adjacent to the opening edges of the doors, further means of the kind stated nearer to the hinged edges of the doors. This increases the cost and complicates the opening and closing operations. In certain cases then, to achieve satisfactory results different means for the purpose aforesaid must be used intermediate the hinged edges of the doors and the means of the kind stated.